Development of molecules exhibiting slow relaxation of magnetization has been an active area of research for more than 25 years.[1] These single-molecule magnets (SMMs) hold promise for high density information storage, quantum computing and spintronics applications. More recent focusing on lanthanide-based single ion magnets (SIMs) has been a particularly worthwhile endeavor as it led not only to discovery of the best performing SMMs to date, but also to further elaboration of organolanthanide chemistry. The latter stems from the fact that classical organometallic ligands such as cyclopentadienide and cyclooctatetraenide (COT) align well with the theoretical design principles for achieving superior SIMs.

Heterogenization of these molecular complexes has received much less attention in the literature, despite its paramount importance from the perspective of practical implementation in devices.[2] Most of the work done to date explored the non-covalent deposition of known SMMs on metal surfaces, but such immobilization strategy typically leads to a sharp decrease of magnetic performance presumably due to a perturbation of the desired metal geometry/electronics and a misalignment of magnetization easy-axes upon grafting. While direct covalent attachment of SMM could in principle provide more control over directionality, it has so far been hardly explored.

In this contribution we demonstrate that covalent grafting of an established COT-based SIM on the surface of partially dehydroxylated silica through surface organometallic chemistry (SOMC)[3] can significantly improve its magnetic performance. This approach allows us not only to maintain hysteretic behavior of the parent system, but also provide magnetic site separation and increase the relaxation time by two orders of magnitude. With the preeminence of organolanthanide systems our approach holds promise for broader applicability in the field.

Acknowledgements:
The authors acknowledge ERC MULTIPROSMM project (grant no. 725184); MDK would like to thank ETH Zurich Postdoctoral Fellowships program (FEL-23 19-1).

[1] Layfield, R. A. Organometallics, 2014, 33, 1084.
[2] Holmberg, R. J.; Murugesu, M. J. Mater. Chem. C, 2015, 3, 11986.
[3] Copéret, C.; Comas-Vives, A.; Conley, M. P.; Estes, D.; Fedorov, A.; Mougel, V.; Nagae, H.; Núñez- Zarur, F.; Zhizhko, P. A. Chem. Rev., 2016, 116, 323.